Change placeholder text at run time

you can use getElementsByName() method to select the input fields and to change the placeholder for each one... see the below code...

document.getElementsByName('Email')[0].placeholder='new text for email';

document.getElementsByName('First Name')[0].placeholder='new text for fname';

document.getElementsByName('Last Name')[0].placeholder='new text for lname';

 type="text" name="First Name" placeholder="Some Text"/>   

document.getElementsByName('First Name')[0].placeholder='new text for fname';

If you wanted to replace all placeholder text from whole site. add below code in your js file, this will change 

$(document).ready(function()

{   

$('form').find("input[type=textarea], input[type=password], textarea").each(function(ev) 

{ if(!$(this).val()) 

{       

$(this).attr("placeholder", "Type your answer here"); 

} }); });